Background: Discontinuation of denosumab treatment causes an increase in bone resorption that has been linked to the emergence of vertebral fractures.

Objectives: To evaluate the association of clinical features and demographic characteristics with the emergence of new fragility fractures in patients with osteoporosis who interrupt treatment with denosumab.

Methods: Retrospective case-control study. Medical records of all patients with osteoporosis, from our local densitometry database, who received treatment with denosumab (at least one dose) and discontinue the treatment, have been studied.

Information was collected on demographic variables (age, sex), risk factors for osteoporosis (alcohol and tobacco consumption, personal history of fragility fracture and history of maternal hip fracture), secondary osteoporosis (due to early menopause, disease or osteopenizing treatment), previous treatment for osteoporosis, start and end date of denosumab treatment and subsequent treatments.

All patients who suffered a fragility fracture from 6 months after the last dose of denosumab up to 20 months later were defined as a case. Prior treatment with bisphosphonate was considered to those who had received it for at least 1 year, and subsequent treatment with bisphosphonate was considered to those who received it immediately or up to 8 months after the last dose of denosumab.

Results: In total, 63 patients who discontinued treatment with denosumab were included. Ten of them presented fragility fractures (6 vertebral, 3 forearm and 1 hip). Two patients had a fracture after 24 months of the last dose of denosumab, so don’t were considered cases. 61 patients were women (96.83%) and the mean age (SD) was 70.22 (8.95) years. The mean time (SD) of treatment with denosumab was 42.25 (17.32) months, with a mean (SD) doses of 7.85 (2.78). The reasons for interruption of denosumab were: improvement 39 (65%), dental procedure 9 (15%), patient decision 6 (10%), adverse event 4 (6.66%) and inefficacy 2 (3.33%). Demographic and clinical features by fragility fracture are shown in Table 1. We found that subsequent treatment with bisphosphonates after denosumab was initiated in less patients in the fracture group than in the control group (10% vs 42,9%; p=0,05), and we found no fractures in patients diagnosed with secondary osteoporosis. No statistically significant differences were found in the rest of the variables.

Conclusion: Sequential treatment with bisphosphonates and diagnosis of secondary osteoporosis are related to the absence of fractures after discontinuation of denosumab treatment.

Acknowledgments: This study was supported by a research grant from Asociación para la Investigación en Reumatología de la Marina Baixa (AIRE-MB).

Disclosure of Interests: None declared